RINSE the split peas.
MINCE the onion. In a saucepan, add the olive oil and fry the onions without browning.
ADD the split peas, thyme, fennel, and 3 parts water. Cook slowly, covered, for 1 to 1 hour 15 minutes, watching for evaporation. Season.
STOP cooking, remove the thyme and fennel. Add the lemon zest and juice. Drain, reserving the broth.
BLEND in a food processor with a spoonful of olive oil. Add broth if necessary.
Enjoy with breadsticks or on slices of country bread!